Different construction principles have become known for the releasable mounting on rotatable reel supports or hubs of reels for the uptake of tape-like information carriers. It is the aim of a series of known arrangements to achieve this type of mounting in an automatic manner, that is to say, without actuation of a control element or without making use of any auxiliary force. Such types of arrangements are easy to handle and reduce the risk of damage to the tape, which risk, in the presence of a separate actuating element, is always present due to the fact that the actuation of the latter can be overlooked and that the reel, which is disposed only loosely on the hub, may then give rise to slacknesses in the tape.
An arrangement of the initially mentioned type is known, for example, from the German DT-AS no. 19 12 076. In that publication, a stud is provided with two adjacently disposed, shallow annular slots, between which a flexible, tensioned ring is rolled back and forth when the tape reel is being pushed on, or being removed. The mutual distances of the annular slots and the distances between the annular slots from the reel-supports, as well as the cross-sectional circumference of the flexible ring are selected in such a manner that the pushed-on reel is pressed in a resilient manner against the reel-support. However, in the case of this arrangement, it can hardly be avoided, that after a relatively large number of mountings, the flexible ring is twisted in itself, so that, under certain circumstances, the reel is not pressed with sufficient force over its entire periphery against the reel-support. Furthermore, also in view of the tolerances during the manufacture of flexible rings, as well as in view of aging processes, wear and tear and temperature influences, there is no guarantee that the operating behavior of this arrangement remains sufficiently uniform and reliable over relatively longer periods of time.
In the case of another arrangement known from the DT-AS no. 19 14 476, the hub is divided into an inner and outer hub-part. The inner hub-part includes a truncated cone surface on which, during the inward displacement of the outer hub-part, a number of pins, which are uniformly distributed along the periphery of the outer hub part, and which radially slide in the cylinder wall, are moved outwardly. Into an annular ring slot at the exterior of the periphery of the exterior hub part, a flexible ring is inserted, which is frictionally connected with the tape-reel. A snap-spring holds the two hub parts together in their end positions, and connects them in a torsion-resistant manner. Although this arrangement eliminates an essential disadvantage of the above described arrangement, namely the tendency of the flexible ring to become twisted, its proper functioning likewise depends on the characteristics of the ring, such as flexibility and form stability, which characteristics can become lost. Furthermore, the reel is not pressed in a resilient manner against the reel support, so that it can wobble.
Furthermore, an arrangement for an automatic assurance of the proper mounting of a reel used in conjunction with recording tapes has become known (DT-AS no. 21 58 862), in the case of which rocker arms, when mounting the reel on top of the reel-support, rock over from a first stable take-up position, while overcoming a dead center, to a second stable holding position. However, the claw-like construction of the rocker arms requires a particular construction of the reel take-up bore, so that the standard tape reels with even boreholes, which are available in large quantities, cannot be used with this arrangement. Furthermore, special precautions have to be taken for the accurate transfer of the rotational momentum from the reel-support to the reel. Moreover, the known arrangement has a heavy intrinsic weight, which is particularly disadvantageous in cases of portable instruments.